Method and apparatus for exhausting vacuum-tube-lamp envelopes



Aug; 7, l 928. 1,679,383

R. c. SMALLEY METHOD AND APPARATUS FOR EXHAUSTING- VACUUM TUBE LAMP ENVELOPE-S Filed June. 2, 1926 ROBERT C. SMALLEY WWW Patented Aug. 7, 1928.-

UNITED STATES ROBERT C. SMALLEY, OF ARLINGTON, NEW JERSEY.

METHOD AND APPARATUS FOR EXHAUSTING VACUUM-TUBE-LAMP ENVELOPIB Application filed June 2, 1926. Serial No. 113,307.

This invention relates to vacuum tube lamps such for example as the well known neon lights in which a column of more or less rarefied gas such as neon contained in a transparent envelope is caused to glow by the passage of an electric current therethrough, and more particularly it relates to a method and apparatus for exhausting the envelopes for said lamps.

It is an object of this invention to provide an improved method and apparatus for exhausting lamp envelopes having relatively small service electrodes, such as those in which a foreign substance as for example a metal or metals of the alkali or alkali earth group are to be introduced to enable operation of the tube with relatively small service electrodes.

The features of novelty which I believe to be characteristic of my invention are po1nted out with particularity in .the appended claims. My invention itself however, both as to its underlying principles and as to its practical embodiments, will best be understood by reference to the specification and accompanying drawing in which:

Figure 1 represents a lamp envelope during exhaustion in accordance with my mvention; and

Figure 2 the lamp in its final form.

- It has been found that the cathode drop or the potential diflerence existing between the negative electrode or cathode, and the column of gas during illumination may be decreased by the introduction of certain substances into the tube. Among these sub stances may be mentioned metals of the alkali and alkali earth group such for example as sodium, potassium, caesium and the like. If such substances are introduced the service electrodes may be made materially smaller without decreasing the operating life of the lamp, and other advantages may be realized with which I am not here concerned.

In the process of exhausting the lamp envelopes in manufacturing such vacuum tube lights it is necessary not only to remove the air from the lamp envelope by means of pumps as far as possible but also to remove occluded gases from the interior walls ofthe envelope and from the electrodes. These occluded gases are usually removed by heating the tube during the exhaustion, the heating liberating the occluded gases and the pump removing them.-

The preferred way of heating the tube to drive ofi occluded gases is to pass an electric current throu h the interior of the tube from one electrode to the other in much the same way in which a current is passed 1n the normal use of the tube. This heating however, cannot be done with tubes in which the service electrodes are relatively small, such as tubes adapted for operation with alkali or alkali earth metals, since the current density necessary to heat the tube to the proper temperature would-result in destruct1on of the electrodes. It has therefore been considered necessary to carry on the heating of such tubes in an oven which has certain disadvantages, among them being that the tube is not accessible during the evacuat1on process for inspection or other purposes.

In accordance with my invention I attach or seal on to the tube a pair of bulbs contaming auxiliary or exhausting electrodes of suflicient size to pass suflicient current to heat the envelope to the desired degree. I then proceed to exhaust the tube by connecting it to a. pump and pumping out all but the residual or occluded gases. I then pass a current through the tube by means of the auxiliary or exhaustin electrodes and also if desired by means of t e service electrodes thereby freeing the'interi'or of the envelope and the service electrodes of any occluded or residual gases. After completion of the exhaustion and the admission of the desired gas such as neon the tube is sealed off from the exhaust line and the auxiliary or exhausting electrodes are likewise sealed 011', after which the tube is ready for use.

Referring now more particularly to Figure 1, 1 designates the envelope to be exhausted provided with operating or service electrodes 2 maintained in place by suitable strings of glass heads 3 strung on wire and carried by lead-in wires 4 passing through a press 5. A connection 6 leads to suitable pumps or other exhausting apparatus not shown. The exhausting or auxiliary electrodes 9 are carried in bulbs 7 which are sealed to the envelope 1 at neck portions 8 for convenient and ready removal. The auxiliary electrodes are, if desired, maintained in position by suitable strings of glass beads 10 strung on wire and the electrode is carried upon lead-in wires 11 passing through a ress 12.

s already described in exhausting the lamp envelope 1 the pump or other exhausting apparatus is started and continued in operation until all free gas has been removed and only the residual or occluded gas remains within the envelope. At this point current may be passed between the auxiliary or exhausting electrodes 9 and simultaneously between the service electrodes 2 and the pumping will be continued under these conditions until the residual gases have been removed to the extent desired, after which the exhaust line (3 may be sealed off by bringing the flame from a Bunsen burner to the junction between the tube 6 and envelope 1 as will be readily understood and similarly the bulbs 7 may be removed and sealed oil from envelope 1 at neck portions 8 leaving the small tips 13.

\Vhile I have shown and described certain preferred embodiments of my invention it will be understood that modifications and changes may be made without departing from the spirit and scope of my invention as will be readily understood by those skilled in the art.

What I claim is:

1. The method of producing a vacuum tube lamp which comprises removing gas from the interior of the lamp envelope while passing an electric current through the tube between a pair of electrodes in said gas, and removing said electrodes after passage of said current.

2. The method of producing a vacuum tube lamp which comprises removing gas from the interior of the lamp envelope while passing an electric current through the tube between a pair of electrodes contained within said envelope, and sealing of]? said electrodes after passage of said current.

3. The method of producing a vacuum tube lalnp which comprises scaling to the lamp envelope a pair of electrodes, passing an electric current through the tube between said electrodes while exhausting said envelope, and sealing oil said electrodes after passage of said current.

4.-The method of producing a vacuum tube lamp containing a pair of operating electrodes which comprises scaling to the lamp envelope :1 pair of auxiliary electrodes, passing current between said auxiliary electrodes through the tube while exhausting said envelope and sealing off said auxiliary electrodes.

5. The method of producing a vacuum tube lamp containing a pair of operating electrodes within said envelope which comprises scaling to the lamp envelope a pair of auxiliary electrodes, passing current through all of said electrodes while exhausting the envelope and sealing oil the auxiliary electrodes.

(5. The method of producing a vacuum tube lamp comprising a pair of operating electrodes which comprises providing the lamp envelope with a plurality of electrodes having an effective area greater than that necessary for final operation, passing current between said electrodes while exhausting the envelope, and removing the excess part of the ell'ective electrode area.

7. The method of producing a vacuum tube lamp comprising a pair of operating electrodes which comprises providing the lamp envelope with a plurality of electrodes having an effective surface area in excess of that desired for final operation, passing current between said electrodes while exhausting said envelope, and removing the excess electrode area after passage of current.

8. Vacuum tube lamp exhausting apparatus com rising, in combination an envelope to e exhausted containing therein a pair of electrodes, a pump connected to said envelope, and a pair of exhausting electrodes separately connected with the interior of said envelope.

9. Vacuum tube lamp exhausting apparatus comprising, in combination, an envelope to be exhausted containing therein a pair of operating electrodes, a pump connected to said envelope, and a pair of exhausting electrodes separately connected with the interior of said lamp envelope in a manner to be readily removable.

10. An envelope for vacuum tube lamps comprising a portion adapted to form the lamp and containing service electrodes therein, and having additional and readily removable portions eaeh containing an auxiliary electrode.

11. An envelope for vacuum tube lamps comprising a portion adapted to form the lamp and containing service electrodes disposed therein, of relatively small area, and having additional and readily removable portions each containing an auxiliary exhausting electrode.

In testimony whereof, I have hereunto set my hand this 21 day of May, 1926.

ROBERT C. SMALLEY. 

